Abstract
Background : Yolk sac tumors (YST) are one of the germ cell tumors producing alpha fetoprotein (AFP) and a relatively rare gonadal tumor occurring at a young age. In the extremely rare cases, it arises in extragonadal sites. We report herein on a case of YST in the mediastinum.
Case : A giant mass in the left lung field was seen on chest X-ray and computed tomography (CT) imaging in a woman in her 20s. Taking the result of aspiration cytology into consideration, we suspected the presence of an undifferentiated malignant tumor. Judging from immunohistochemistry of the cell block, we diagnosed the tumor as a YST. After retrospective observation of the same aspirated specimens, we were able to identify the characteristic cytological findings of a YST such as so-called “balloon animal”-like cell clusters and hyaline globules.
Conclusions : Although finding “balloon animal”-like cell cluster and hyaline globules is valuable in diagnosing YST, it is difficult to identify YST from other similar diseases judging from only these cytological findings. It is very important to make the diagnosis, taking into general consideration results from other examinations, such as HE staining, cell block immunohistochemistry and clinical information.
